Primary creep behaviour of polyester resins from multiple relaxation curves

Abstract

Typical primary creep behaviour of a viscoelastoplastic material is shown when varying the temperature and the time rate of strain (of a previous tension). The creep behaviour is obtained from the tension test with multiple relaxations, where a numerical procedure is used in order to obtain creep curves from a series of relaxation curves. This test methodology allows interrelated tension, relaxation and creep behaviours to be obtained from one single test. The materials tested are proportional to the weight mixtures of rigid/flexible polyester resins with hardeners, generally used as model materials in photomechanics. With the increase in temperature, there is a decrease in the time needed to reach a given creep strain. The time rate of the strain, used in the tensions prior to the relaxations, has a considerable influence on the beginning of the relaxations. Since the creep curve is obtained from these relaxations, the rate of strain is shown to have an influence on creep behaviour, depending on the portion of the relaxation curve from where values are taken for calculation of creep.

Keywords

mechanical behaviour stress/strain analysis viscoplasticity creep numeric and experimental modelling

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References

Oliveira

L. C.

Study on the characterisation and modelling of the mechanical behaviour in the inelastic-anelastic domain of mixtures of polyester resin (in Portuguese). PhD thesis, Federal University of Uberlândia, Uberlândia, Brazil, 2000.

Souza

S. A.

Mechanical Testing of Metallic Materials: Theoretical and Practical Fundaments (in Portuguese), 1982, 5th edition (Edgard Blücher, São Paulo, Brazil).

McClintock

F. A.

Argon

A. S.

Mechanical Behaviour of Materials, 1966 (Addison-Wesley, Reading, Massachusetts).

Kraus

Creep Analysis, 1979 (John Wiley, New York).

Lemaitre

Chaboche

J.-L.

Mechanics of Solid Materials (in French), 1985 (Bordas, Paris).

Lemaitre

On the determination of the behaviour laws for elastoviscoplastic materials (in French). PhD thesis, University of Paris XI (Orsay), Paris, France, 1971.

Belhedi

Preliminary study for the understanding of a certain class of behaviour laws (in French). DEA dissertation, University of Franche-Comté, Besançon, France, 1988.

Maire

J. F.

Theoretical and experimental studies of the behaviour of composite materials in plane stress (in French). PhD thesis, University of Franche-Comté, Besançon, France, 1992.

Rade

R. S. L.

A comparative study of two models of viscoplastic behaviour with damage for stratified composite materials (in French). PhD thesis, University of Franche-Comté, Besançon, France, 1994.

10.

Morris

D. H.

Riley

W. F.

A photomechanic material for elastoplastic stress analysis. Expl Mechanics, 1966, 12(10), 448–453.

11.

Siqueira

R. C.

Gomide

H. A.

Identification of the elastoplastic properties of photoplastic materials (in Portuguese). In III CME-NNE, 1994, pp. 504–512.

12.

Oliveira

L. C.

Gomide

H. A.

Rade

R. S. L.

Determination of the viscoplastic characteristics of a polyester resin mixture. In Proceedings of the XIV COBEM, Bauru, Brazil, 1997 (in CD).

13.

Oliveira

L. C.

Gomide

H. A.

Rade

R. S. L.

Basic modelling of the viscoplastic characteristics of a mixture of resins (in Portuguese). In Proceedings of the V CEM-NNE, Fortaleza, Brazil, 1998 (in CD).

14.

Oliveira

L. C.

Gomide

H. A.

Rade

R. S. L.

Viscoplastic modelling of the strengthening and relaxation of a polyester resin. In Proceedings of the VIPACAM, Rio de Janeiro, Brazil, 1999.

15.

Oliveira

L. C.

Gomide

H. A.

Rade

R. S. L.

Basic formulation for the mechanical behaviour in viscoplastic experiments (in Porceedings of the XVI COBEM, Uberlândia, Brazil, 2001.

16.

Oliveira

L. C.

Gomide

H. A.

Rade

R. S. L.

Phenomenological behaviour of mixtures of photovisco-plastic resins. Sci. Engng J., 2000, 9(2), 102–109.

17.

Oliveira

L. C.

Gomide

H. A.

Rade

R. S. L.

Obtaining creep behaviour from multiple relaxation tests in polyester resins (in Portuguese). In Proceedings of the CNEM 2002, João Pessoa, Brazil, 2002.